Ground pegs serve to anchor objects such as columns or support frames in the ground. Thus, for example, solar collectors outdoors are often anchored in the ground with such ground pegs.
Such ground pegs exist in numerous different versions and dimensions. They normally consist of a tube section that has a constant diameter over a certain length. The lower section of the ground peg is conically tapered so that the ground peg can be screwed into the ground and can thus be firmly secured by displacing the soil. In order for the ground peg to be screwed in, it is provided with an external thread that can be formed, for example, by a welded-on sheet metal strip.
The conical section is normally welded onto the cylindrical section. The conical section is usually made out of a cylindrical tube section by means of a cold-forming method, so-called kneading or hammering. The lower tip can be formed, for example, by a welding and/or forging process. The external thread normally extends from the lower part of the cylindrical tube section past the conical section, reaching almost all the way to the lower tip.
Support columns or the like can then be slid into the tube section and affixed, usually by means of clamping screws, at the top, open end of the ground peg that extends slightly out of the ground.
A ground peg with a hammered conical section and a method for its production are disclosed in German patent application DE 198 36 370 A1. The body of this ground peg has a conical basic shape and a conical partial section. The body is produced by hammering a previously cylindrical tube. A similar ground peg with a hammered anchoring section is known from German utility model DE 299 23 796 U1.
The external threads of the prior-art ground pegs are wound and brought into the desired shape, they are subsequently slid over the circumferential surface in the lengthwise direction starting from the tip, and welded onto the surface. In the case of minor dimensional deviations, this can easily result in jamming or locking of the thread. Moreover, the pitch of at least the lower tapered section usually differs somewhat from the pitch of the other sections. The welding of the external thread is normally done by hand, and so are most of the other production steps, for example, the welding of the two tube sections of the ground peg, so that the production of the entire ground peg turns out to be very labor-intensive and thus relatively expensive.
Another problem can occur due to the multi-component structure and thus the resultant weakening in the vicinity of the weld seam. There are normally no problems when such ground pegs are screwed into loose soil. The rigid anchoring is achieved through the displacement of the soil by the ground peg as it is being screwed into the ground by means of its thread. In this manner, the ground peg can offer a play-free and very sturdy anchoring possibility, even with relatively loose soil. In the case of very rocky and hard subsoil, however, these ground pegs often reach the limits of their strength, and they tend to fail due to breakage, especially in the area where the cylindrical tube section is joined to the kneaded conical section. At a typical tube diameter of approximately 50 mm to 100 mm, a steel tube can have a wall thickness between approximately 1.5 mm and 2.5 mm. Since the same starting material is also used for the kneaded conical lower section, the wall thickness increases markedly downwards toward the tip, whereas in the upper area, near the weld seam, it is likewise only between 1.5 mm and 2.5 mm. Consequently, the conical section does not yield under high loads, but rather, it is especially torsionally stiff. However, on the other hand, since the conical section is subjected to the greatest torsional loads while the ground peg is being screwed into very hard subsoil, this load is almost completely transmitted to the upper area and to the weld seam, so that the latter tends to crack under very high loads.